Working hours and depressive symptoms: the role of job stress factors

BACKGROUND: South Korea is one of the countries with the longest working hours in the OECD countries. The aim of this study was to evaluate the effect of working hours on depressive symptoms and the role of job stress factors between the two variables among employees in South Korea. METHODS: This study used data from the Korea Working Conditions Survey in 2014. Study subjects included 23,197 employees aged 19 years or older who work more than 35 h per week. Working hours were categorized into 35–39, 40, 41–52, 53–68, and more than 68 h per week. Depressive symptoms were assessed using the WHO’s Well-Being Index with a cut-off score of 13. We calculated prevalence ratios of depressive symptoms according to working hours using log-binomial regression. Through the percentage change in prevalence ratios, we identified the extent of the role of job stress factors that explain depressive symptoms. RESULTS: The risks of depressive symptoms were significantly higher in people who worked 35–39 h per week (PR: 1.09, CI: 1.01–1.18), 53–68 h/week (PR: 1.21, CI: 1.16–1.25), and more than 68 h/week (PR: 1.14, CI: 1.07–1.21) than 40 h/week, after adjusting for confounding variables. Job stress explained the effects of long working hours on depressive symptoms in about 20–40% of the groups working more than 40 h/week. Among the factors of job stress, social support was 10–30%, which showed the highest explanatory power in all working hours. Reward explained 15–30% in the more than 52 h working group, and reward was the most important factor in the working group that exceeded 68 h. CONCLUSIONS: We showed the working hours could be an independent risk factor for depressive symptoms in employees. To improve workers’ mental health, it is important to strengthen social support in the workplace, to provide adequate rewards as they work, and ultimately to regulate the appropriate amount of working hours.

Toxicity of Methylcyclohexane and Its Effect on the Reproductive System in SD Rats

OBJECTIVES: There is limited data regarding the toxicity of methylcyclohexane, despite its wide use in rubber adhesives, paint diluents, and cleansing agents. This study aimed to verify the toxicity and influence on the reproductive system of methylcyclohexane after its repeated injection in Sprague Dawley (SD) rats. METHODS: Methylcyclohexane was injected subcutaneously into male and female SD rats once a day, five times a week, for 13 weeks at different doses (0, 10, 100, and 1,000 mg/kg/day) for each group. The toxicity of testing material was verified by observing the change in body and organ weight, hematological change, pathological findings, and effect on the reproductive system at each different concentration. RESULTS: In the 1,000 mg/kg/day group, there were cases of animal deaths. In animals that survived, hematological changes, including a decrease in the red blood cell count, were observed. A considerable weight gain or loss and pathological abnormalities in the liver, kidney, and other organs were found. However, the 10 and 100 mg/kg/day groups did not cause deaths or other specific abnormalities. In terms of reproductive toxicity, there were changes in hormone levels, including a significant decrease in hormones such as estradiol and progesterone (p < 0.001) in male animals. Menstrual cycle change for female animals did not show concentration dependency. CONCLUSION: When injected repeatedly for 13 weeks, methylcyclohexane proved to be toxic for the liver, heart, and kidney at a high dose. The absolute toxic dose was 1,000 mg/kg/day, while the no observed adverse effect level was less than 100 mg/kg/day. The substance exerted little influence on the reproductive system.

Hot Tub Lung Due to Mycobacterium Avium Complex in a Public Bath / 대한산업의학회지

BACKGROUND: Hot tub lung is a hypersensitivity pneumonitis caused by nontuberculous mycobacteria (NTM); the primary causative agent is Mycobacterium avium complex (MAC) post contaminated water exposure. Recently, 2 cases of hot tub lung were found in public bath bodyscrubbers working in Korea. However, the disease causing NTM was not identified in these cases. Here, we reported one case, along with clinical diagnostic approach to occupational medicine throughout worksite investigation. CASE: A 53 year-old woman working in the public bath for 13 months' duration developed shortness of breath. She had been cleaning the locker room, several pools and floors every day, and using scrubbers with detergent and warm water. After examination, the patient was diagnosed with hypersensitivity pneumonitis based on high resolution computerized tomography and lung biopsy. Because the Mycobacterium avium was identified in both the patient's sputum and the warm pool, she was diagnosed with hot tub lung due to MAC. CONCLUSION: Hot tub lung due to MAC was confirmed in public bath housekeeper. However, few cases have been reported, even though there are many cases. To prevent damages caused by hot tub lung, general environmental management such as ventilation and cleaning is important for bath operators. Likewise, awareness needs to be increased in workers with potential NTM environmental exposure and in clinicians through education about hot tub lung in order to reduce adverse harm from misdiagnosis and mistreatment of tuberculosis.

The Effects of Particulate Matter on Respiratory Function of Schoolchildren in Jeju: A Panel Study / 대한산업의학회지

OBJECTIVE: To evaluate the changes in respiratory function associated with daily changes in particulate pollution. METHODS: A total of 105 healthy schoolchildren of fourth and fifth grade elementary school age performed peak expiratory flow rates (PEFR) during 2 periods (May 14~June 15, Oct 22~Nov 23). We monitored concomitant ambient particulate matter (PM) levels during the periods. RESULTS: An elevation PM(10) level of 1 microgram/m) led to decreases in PEFR of 0.20 L/min. A 1 microgram/m3 elevation of PM(2.5) led to a decrease of 0.36 L/min in PEFR. In addition, 1 day lag was associated with PM(10) levels and PEFR changes, and PM(2.5) showed the same result. The metal levels determined at PM(10) and PM(2.5) were found to be associated with decreased respiratory function. CONCLUSIONS: An association between respiratory function and particulate pollution was observed when particulate pollutant levels were lower than the yearly average National Ambient Air Quality Standard in the Korea(50 microgram/m3).